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Configuring Gigabit Ethernet Two-Color and Tricolor Policers
For Gigabit Ethernet and 10-Gigabit Ethernet IQ2
interfaces on M-series and T-series routing platforms, you can configure
two-color and tricolor marking policers and apply them to logical
interfaces to prevent traffic on the interface from consuming bandwidth
inappropriately.
Networks police traffic by limiting the input or
output transmission rate of a class of traffic on the basis of user-defined
criteria. Policing traffic allows you to control the maximum rate
of traffic sent or received on an interface and to partition a network
into multiple priority levels or classes of service.
Policers require you to apply a burst size and
bandwidth limit to the traffic flow, and set a consequence for packets
that exceed these limits—usually a higher loss priority, so
that packets exceeding the policer limits are discarded first.
Juniper Networks routing platform architectures
support three types of policer:
- Two-color policer—A two-color policer (or “policer”
when used without qualification) meters the traffic stream and classifies
packets into two categories of packet loss priority (PLP) according
to a configured bandwidth and burst-size limit. You can mark packets
that exceed the bandwidth and burst-size limit in some way, or simply
discard them. A policer is most useful for metering traffic at the
port (physical interface) level.
- Single-rate tricolor marking (srTCM)—A single-rate
tricolor marking policer is defined in RFC 2697, A Single
Rate Three Color Marker, as part of an assured forwarding
(AF) per-hop-behavior (PHB) classification system for a Differentiated
Services (DiffServ) environment. This type of policer meters traffic
based on the configured committed information rate (CIR), committed
burst size (CBS), and excess burst size (EBS). Traffic is marked as
belonging to one of three categories (green, yellow, or red) based
on whether the packets arriving are below the CBS (green), exceed
the CBS (yellow) but not the EBS, or exceed the EBS (red). Single-rate
TCM is most useful when a service is structured according to packet
length and not peak arrival rate.
- Two-rate Tricolor Marking (trTCM)—This type of policer
is defined in RFC 2698, A Two Rate Three Color Marker, as part of an assured forwarding (AF) per-hop-behavior (PHB) classification
system for a Differentiated Services (DiffServ) environment. This
type of policer meters traffic based on the configured CIR and peak
information rate (PIR), along with their associated burst sizes, the
CBS and EBS. Traffic is marked as belonging to one of three categories
(green, yellow, or red) based on whether the packets arriving are
below the CIR (green), exceed the CIR (yellow) but not the PIR, or
exceed the PIR (red). Two-rate TCM is most useful when a service is
structured according to arrival rates and not necessarily packet length.
Unlike policing (described in Configuring Gigabit Ethernet Policers), configuring two-color policers and tricolor
marking policers requires that you configure a firewall filter.
This section contains the following topics:
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